using jar export in Eclipse 3.0

I am trying to build an App that reads Excel files. I'm using Eclipse 3.0 and the POI API. Everything works when I launch from within Eclipse, but once I export to an executable jar and try to run it the class that uses POI does not seem to work.

I have the POI jar included in my libraries for this project and have played around with the order in the Order and Export TAB in Project Properties menu.

First time using classpath. I have poi.jar in my class bath. But when I try to open the Excel sheet after starting my jar I get "NoClassDefFoundError" and then it lists the fisrt class I try to use in my code.